James P. O'Shea Graduate Student University of California, Berkeley Vision Science Program Visualization Lab Banks Lab 505 Minor Hall University of California, Berkeley Berkeley, CA 94720-2020 joshea (at) cs.berkeley.edu

home | education | conference papers | journal articles | course projects | teaching | professional activities Toward an Objective Characterization of an Anhedonic Phenotype: A Signal-Detection Approach Diego A. Pizzagalli, Allison L. Jahn, and James P. O’Shea Background: Difficulties in defining and characterizing phenotypes has hindered progress in psychiatric genetics and clinical neuroscience. Decreased approach-related behavior and anhedonia (lack of responsiveness to pleasure) are considered cardinal features of depression, but few studies have used laboratory-based measures to objectively characterize these constructs. Methods: To assess hedonic capacity in relation to depressive, particularly anhedonic, symptoms, 62 participants completed a signal-detection task based on a differential reinforcement schedule. Anhedonia was operationalized as decreased reward responsiveness. Results: Unequal frequency of reward between two correct responses produced a response bias (i.e., a systematic preference to identify the stimulus paired with the more frequent reward). Subjects with elevated depressive symptoms (Beck Depression Inventory scores > 16) failed to show a response bias. Impaired reward responsiveness predicted higher anhedonic symptoms 1 month later, after controlling for general negative affectivity. Conclusions: Impaired tendency to modulate behavior as a function of prior reinforcement might underline diminished hedonic capacity in depression. When applied to a clinical population, objective assessments of participants’ propensity to modulate behavior as a function of reward might provide a powerful tool for improving the phenotypic definition of depression and thus offer a reliable behavioral screening approach for neuroscience studies of depression. Mean response bias for subjects with high (black bars; n=15) and low (light gray bars; n=21) Beck Depression Inventory (BDI) scores. Error bars represent standard errors. Research Paper: PDF Toward an Objective Characterization of an Anhedonic Phenotype: A Signal-Detection Approach Diego A. Pizzagalli, Allison L. Jahn, and James P. O’Shea Biological Psychiatry 2005; 57: 319-327. home | education | conference papers | journal articles | course projects | teaching | professional activities